Scientists have to figure out how to solve all kinds of problems that seem like they shouldn’t be problems until you think about them.

So, how do you describe a color so I know the exact shade you’re talking about?

Sure, we know navy blue, which most of us know as a distinct shade of dark blue. And we have fire-engine red, which most of us would also recognize.

But.

What if you’re an archaeologist carefully digging in the soil, and you pick up your notebook and you want to describe the exact shade of yellowy-browny-beige soil that you have just exposed. How do you do that so, even twenty years later, a reader will know just what color that soil was?

Well, use a Munsell Soil Color Chart!

These charts are published in special (expensive!) books with little carefully made color chips on each page. You take a small soil sample and hold it behind the page and move it around until you see it through a hole that’s next to a color that’s identical to it. Thus, Munsell Soil Color Charts provide a standard way of identifying colors.

An archaeologist who has excavated across the Georgia piedmont will recognize that 10YR5/4 refers to a soil of a particular, pleasant medium-brown hue. That color is on the chip in the fourth row from the top, and fourth chip from the left in this picture.

10YR refers to a certain saturation or brightness of yellow-red (the YR part). The five refers to a medium darkness, and the four refers to how yellowy the brown is.

Got it?

For technical information about how the colors have been determined, check this web page on the US Department of Agriculture website.